28 PROCEEDINGS OP THE AMERICAN ACADEMY 



For determining these facts, the apparatus represented upon plates 

 No. 1 and No. 2 was constructed. It consisted of a straight trough 

 thirty feet long, of uniform section, one foot deep and three-tenths of 

 a foot wide inside, receiving water at A from a chamber four feet 

 wide. At a distance of six-tenths of a foot up stream from the 

 entrance was a gate B, which, being opened, connected the chamber 

 with a penstock four feet wide, six feet high, and two hundred feet 

 long, bringing water from the Essex Company's south canal. The 

 down-stream side of the chamber A was built up to the height required 

 during the several experiments ; and its upper edge used as the crest 

 of a regulating waste weir, over which water continually flowed into 

 the waste trough C, which conducted it outside of the measuring basin. 



The experimenting trough discharged its water at D into the swing- 

 ing conductors, supported by the pivot a, which conveyed it by the 

 branch E directly down into the measuring basin G, or by the branch 

 F into the river, as the partition b was raised above or lowered below 

 the stream. 



The measuring basin G, 15.93 ft. wide, and 36.55 ft. long, and about 

 8 ft. deep, built of timber and planks on a firm foundation, was buried 

 in earth nearly to its full depth, except on the river side, which was 

 held from being pressed outward by a strong truss ; and except at 

 the observer's house H, where the heights of water in the basin were 

 observed. 



The area of the measuring basin, within the range of filling during 

 the experiments, which was between 4.5 ft. and 6.5 ft. above the bot- 

 tom, was, deduction being made for all supporting timbers for the 

 upper works, found to be 570 square feet. 



The depths of water in the measuring basin were measured by 

 means of a hook gauge in the box c, which was in free communication 

 with different parts of the basin by three pipes, 0.083 ft. in diameter. 



The hook gauge used is described and illustrated in " Lowell 

 Hydraulic Experiments," * page 18. 



Water was drawn from the measuring basin through the waste 

 gate d. 



The experimental trough was at first placed level, having firm bear- 

 ings about ten feet apart. The upper end was connected with the 

 chamber A with a lining of rubber, making a water-tight joint, which 

 continued water-tight when the other end of trough was lowered 



* Lowell Hydraulic Experiments. By James B. Francis, C. E., &c. Third 

 Edition. New York : D. Van Nostrand. 1871. 



